Fixing cover

ABSTRACT

A bolt head cover ( 10 ) comprises an outer heat resistant portion ( 12 ) and an inner gripping portion ( 14 ). The bolt head cover ( 10 ) is arranged to be placed over the bolt head ( 16 ). The bolt head cover ( 10 ) is retained in position by means of the inner gripping portion ( 14 ) which grips the bolt head, with the gripping portion ( 14 ) being retained in the heat resistant portion ( 12 ) by means of flanges ( 18 ).

This invention relates to a fixing cover, and particularly, but notlimited to, a heat resistant cover for a nut or bolt.

A current technique employed for building structures is to use aframework of steel beams. The beams are secured together by means of nutand bolt fixings. It is important that the nut and bolt fixings areprotected from heat damage in the event of a fire. An existing method ofprotecting the nuts and bolts from excessive heat is to paint the nutsand bolts with an intumescent material. This material is fire resistantand to some extent prevents the failure of the nut and bolt joints inthe event of a fire.

However, disadvantages arise with this method, because it is difficultto check visually that the correct type of intumescent material has beenused. It is sometimes the case that the nuts and bolts are simplypainted over with material of a similar colour to the correctintumescent material. This results in an extremely dangerous possibilitythat the joints of the steel structure could fail during a fire, leadingto collapse of the building.

It is an object of the present invention to address the above mentioneddisadvantages.

It is a further object of the present invention to provide means forproviding heat protection to steel structure fixings and means forvisually indicating that those fixings are protected.

It is a still further object of the invention to provide a protectivecover for a joint fixing which in use allows for expansion of said jointfixing.

According to one aspect of the present invention a protective cover fora joint fixing comprises fixing gripping means and fire resistant covermeans, wherein the gripping means are resiliently biased for gripping afixing and for allowing expansion of a fixing during heating.

The fixing may be a bolt or a nut or a nut/bolt combination. The fixingmay be a fixing for a structure made of metal beams.

The gripping means may be adapted to allow expansion of a fixing withinthe cover means. In which case the cover means may be substantiallyresistant to significant heat expansion of the fixing.

The cover means may be hollow. The cover means may have an opening inwhich to receive the fixing. The cover means may have a domed outersection, which may be opposite the opening in the cover means.

The cover means may have a stepped profile around said opening,preferably to receive a section of the fixing, preferably a washer.

The cover means may comprise a body section, preferably with a generallycircular cross-section, having the opening at one end thereof. The covermeans preferably also includes an end section which is preferablyopposite the opening and preferably closes one end of the body section.

The gripping means may comprise a least one, preferably three, resilientarms. The or each resilient arm preferably extends down an interior faceof the cover portion. The gripping means preferably comprises fixinggripping means on at least one arm.

The fixing gripping means preferably comprise at least one pointdirected away from the opening in the cover portion. The point ispreferably a flange extending from said arm and at an angle to said arm.The fixing gripping means are preferably located at a lower end of saidarm. There are preferably two points on each arm, preferably one at eachside of said arm. The fixing gripping means preferably deter removal ofthe protective cover from a fixing by means of the or each pointembedding in or being urged against said fixing.

The gripping means preferably comprises cover portion gripping means onat least one arm.

The cover portion gripping means preferably comprise at least one pointdirected towards the opening in the cover portion, preferably away fromthe fixing gripping means. The or each point is preferably a flangeextending from said arm and at an angle to said arm. The fixing grippingmeans are preferably located towards an upper end of said arm. There arepreferably two points on each arm, preferably one at each side of saidarm. The cover portion gripping means preferably deter removal of thefixing gripping means from the cover means by means of the or each pointembedding in or being urged against the cover means.

The direction in which the points of the cover portion gripping meansface may permit the fixing gripping means to be pushed into the covermeans but may resist the same being pulled therefrom.

Preferably, the fixing gripping means comprises three generally flatarms, preferably extending away from each other and generallyequidistant or equispaced to each other. The arms preferably definethree non-adjacent sides of a hexagon to receive a hexagonal nut/bolthead therein. The flat arms preferably extend across the closed end ofthe cover means and down the inner walls of the cover means.

According to another aspect of the present invention a method ofprotecting a joint fixing against excessive heat comprises attaching aprotective cover to the joint fixing by means of gripping means of thecover which are resiliently biased to grip the joint fixing, saidresilient bias of the gripping means also allowing for expansion of thejoint fixing, and in which a fire resistant cover means covers thegripping means and the joint fixing to protect the same from excessiveheat.

All of the features disclosed herein can be combined with any of theabove aspects, in any combination.

A specific embodiment of the present embodiment of the present inventionwill now be described, by way of example, with reference to theaccompanying drawings, in which:

FIG. 1 is a partially cut away side view of a nut/bolt head protectioncap fitted to a bolt head;

FIG. 2 is a cross sectional view from above of the bolt head/nut cover;and

FIG. 3 is a partial side view of a flange of the bolt head/nut cover.

In this description a bolt head cover 10 may occasionally be referred toas a nut cover 10 and the two terms are interchangeable, since the coverreferred to is suitable for being placed over a bolt head and acorresponding nut.

A bolt head cover 10 comprises an outer heat resistant portion 12 and aninner gripping portion 14. The bolt head cover 10 is arranged to beplaced over a bolt head 16. The bolt head cover 10 is retained inposition by means of the inner gripping portion 14 which grips the bolthead, with the gripping portion 14 being retained in the heat resistantportion 12 by means of flanges 18.

In more detail, the inner gripping portion 14 is made of a metal whichcan flex and has some spring characteristics to allow for elasticdeformation of the arms 20 a, b, c, as will be described below.

The gripping portion 14 comprises three arms 20 a, 20 b and 20 c. Thethree arms extend away from a central point 22 such that they have equalangles therebetween. The arms are arranged at the equal angles so thatthe inner gripping portion can be placed over a hexagonal bolt head 16,thereby allowing three (non-adjacent) spaced faces of the hexagonal bolthead 16 to be gripped, as will be described below.

Each arm 20 a, 20 b and 20 c, has a generally flat cross-section andextends horizontally away from the centre point 22 to a first shoulder24 and then to a second shoulder 26. The shoulders 24 and 26 allow thegripping portion to generally follow an inner face of the heat resistantportion 12, as will be described below.

At the second shoulder 26 each arm extends vertically down an inner wallof the heat resistant portion 12.

The flanges 18 are located on this vertical section of each of the arms20, 20 b and 20 c. A first flange 18 a comprises a downwardly extendingpoint 28, as can be seen in FIG. 3. The flange 18 a extends outwardlytowards the inner face of the heat resistant portion 12 and is arrangedto engage said inner face of the heat resistant portion 12 to therebyhold the inner gripping portion 14 in position within the heat resistantportion 12. Because the flange 18 points downwards it prevents thegripping portion 14 being pulled out of the cover portion 12, but allowsthe gripping portion 14 to be pushed into the cover portion 12.

There is a corresponding flange 18 b at the opposite side of each arm 20a, 20 b, 20 c (see FIG. 2), so that each arm has a downwardly extendingpoint 28 at each side thereof. The spring quality of the metal fromwhich the gripping portion is made allows the arms 20 a, b, c and theflanges 18 a and 18 b to maintain pressure against the inner face of theheat resistant portion 12 to thereby maintain the gripping action.

At the base of each arm 20 a, 20 b, 20 c there are flanges 30 a and 30b, one at each side of each arm. These flanges extend inwards and have apoint 32 which is directed upwards, in a similar fashion to which thepoints 28 on the flanges 18 a and 18 b point downwards. The purpose ofthe flanges 30 a, 30 b is to grip the bolt head 16 when the bolt headcover 10 is pushed onto the bolt head 16.

The heat resistant portion 12 comprises a cylindrical wall portion 34and a domed upper portion 36. It is across the inside of the domed upperportion 36 that the upper parts of the arms 20 a, 20 b and 20 c extend.The lower parts of the arms 20 a, 20 b and 20 c extend down the innerwalls of the cylindrical portion 34. There is a step 38 in the lowerpart of the cylindrical portion 34 which provides a recess for the bolthead cover 10 to be placed over a washer 40 as will be described below.

The heat resistant portion 12 is made of a heat resistant plasticsmaterial, such as a cirtam modified polyester dough moulding compound.

The bolt head cover 10 is assembled by pushing the inner grippingportion 14 into the interior of the heat resistant portion 12. The sizeof the inner gripping portion 14, is chosen so that the verticalsections of the arms extend laterally to be just within the inner wallsof the cylindrical portion 34. The flanges 18 a and 18 b extend to aslightly greater diameter than the inner diameter of the cylindricalportion 34 so that when the inner gripping portion 14 is pushed into theheat resistant portion 12 the flanges 18 a and 18 b are flexed inwardly.The resilience of the arms 20 a, b, c and the flanges 18 a and 18 ballows them to retain the inner gripping portion 14 within the heatresistant portion 12. Outward pressure on the inner gripping portion 14will result in the points 28 of the flanges 18 a and 18 b digging intothe material of the heat resistant portion 12 to further retain theinner gripping portion 14 in position.

Once assembled, either on site or before the bolt head cover 10 isdespatched to a site, the bolt head cover 10 is simply pushed onto anexposed bolt head. The flanges 30 a and 30 b have a separation just lessthan the size of the bolt head 16, whereas the remainder of the verticalportion of the arms is just larger than the outer width of the bolt head16, so that when pushed onto a bolt head 16 the arms 20 a, b, c and theflanges 30 a, 30 b deform slightly and thereby grip the bolt head 16.

Should an attempt be made to pull the bolt head cover 10 from the bolthead 16 the points 32 of the flanges 30 a and 30 b will push into thebolt head 16 and deter outward movement of the bolt head cover 10 awayfrom the bolt head 16. Thus, tension will be created between the flanges30 a and 30 b and the flanges 18 a to retain the bolt head cover 10 onthe bolt head 16.

In the event of a fire, the heat resistant portion 12 ensures that thetemperature inside the bolt head cover 10 is considerably lower than thetemperature outside. In one test, the temperature inside the bolt headcover 10 has not passed 550° C. when the temperature outside the bolthead cover has been at 1000° C. for one hour.

In addition, the flexible nature of the gripping portion 14 allows thebolt head or nut to expand within the heat resistant portion 12 bycausing flexure of the gripping portion 14. The expansion does notresult in excessive outward pressure on the heat resistant portion 12because of a gap between the arms 20 a, b, c of the gripping portion 14and the interior of the heat resistant portion 12.

In assembling the bolt head cover 10 it is possible to use adhesive tosecure the lower face 42 of the heat resistant portion 12 to thesurrounding material around the bolt head 16. It is not strictlynecessary to use such adhesive, but additional safety may be provided.In use, it is envisaged that even without the additional adhesiveintumescent material on the surrounding steel beam will rise up thesides of the heat resistant portion 12 to seal any gap which may bepresent between the lower face 42 of the heat resistant portion 12 andthe section of the steel beam up to which it is pushed.

The bolt head 16 may optionally be covered with a corrosion inhibitor,such as a gel, Vaseline, grease or oil based grease. The inhibitorprotects the bolt from the weather or other corrosive factors. In thissituation the bolt cover 10 has the dual advantage of retaining thecorrosion inhibitor and providing a less unsightly bolt head, as well asheat resistance.

In the example shown in the drawings, the heat resistant portion 12 hasa dome with a thickness of approximately 4 mm to 6 mm. In this examplethe side walls have a thickness of approximately 11 to 13 mm, a heightof approximately 28 to 30 mm, with the step 38 having a height of 5 mmand an incut width of approximately 3 mm. The overall external diameterof the cylindrical portion 34 may be approximately 57 mm. The innergripping portion 14 may have arms 20 a, 20 b and 20 c with a width ofapproximately 12 mm. The arms 20 are arranged to grip a bolt head 16 (ora nut) having a diameter of approximately 40 mm.

Of course other sizes of bolt head cover 10 are envisaged, to suit theparticular size of a bolt head. Also, the heat resistant portion 12 maybe thicker where more heat resistance is required.

A further possibility is to have one size of heat resistant portion 12into which one of a variety of sizes of gripping portion 12 can fit.This allows the same heat resistant portion 12 to be used to cover avariety of sizes of bolt/nut, with only the gripping portion 12 changingin each case.

It is a significant advantage of the bolt head cover 10 described abovethat it is self supporting and can be simply pushed on to a bolt head16, with no surrounding material necessary to support the bolt headcover, because of the gripping portion 14.

Also advantageous is the ability to accommodate expansion of a bolt onwhich the cover is placed.

Also, the bolt head cover 10 has the significant advantage of beingreadily visible, even from quite some distance, and that a protectiveheat resistant cover has been secured to a bolt head 16. The bolt headcover provided avoids the possibility that any incorrect intumescentmaterial could be painted onto a bolt head, giving the impression thatthe bolt head is heat protected, when in fact it is not.

The reader's attention is directed to all papers and documents which arefiled concurrently with or previous to this specification in connectionwith this application and which are open to public inspection with thisspecification, and the contents of all such papers and documents areincorporated herein by reference.

All of the features disclosed in this specification (including anyaccompanying claims, abstract and drawings), and/or all of the steps ofany method or process so disclosed, may be combined in any combination,except combinations where at least some of such features and/or stepsare mutually exclusive.

Each feature disclosed in this specification (including any accompanyingclaims, abstract and drawings), may be replaced by alternative featuresserving the same, equivalent or similar purpose, unless expressly statedotherwise. Thus, unless expressly stated otherwise, each featuredisclosed is one example only of a generic series of equivalent orsimilar features.

The invention is not restricted to the details of the foregoingembodiment(s). The invention extend to any novel one, or any novelcombination, of the features disclosed in this specification (includingany accompanying claims, abstract and drawings), or to any novel one, orany novel combination, of the steps of any method or process sodisclosed.

1. A non-removable protective cover for a joint fixing on a steelstructure comprises fixing gripping means for gripping the fixing on thesteel structure and heat resistant, fire resistant cover means forcovering the fixing, wherein the gripping means are resiliently biasedfor gripping the fixing and for allowing expansion of the fixing duringheating, the fixing gripping means comprising at least one firstresilient arm comprising an end point directed away from an opening inthe cover and radially inwardly toward the fixing, and at least onesecond resilient arm comprising an end point directed towards theopening in the cover and radially inwardly away from the fixing, whereinthe end point of the first resilient arm is located closer to theopening than is the end point of the second resilient arm.
 2. Anon-removable protective cover as claimed in claim 1, in which thefixing is a bolt or a nut or a nut/bolt combination for a structure madeof metal beams.
 3. A non-removable protective cover as claimed in claim2, in which the gripping means are adapted to allow expansion of thefixing within the cover means.
 4. A non-removable protective cover asclaimed in claim 1, in which the gripping means are adapted to allowexpansion of the fixing within the cover means.
 5. A non-removableprotective cover as claimed in claim 1, in which the cover means have astepped profile around the opening in which to receive the fixing.
 6. Anon-removable protective cover as claimed in claim 1, in which the oreach resilient arm extends down an interior face of the cover means. 7.A non-removable protective cover as claimed in claim 1, in which thegripping means deter removal of the protective cover from the fixing bymeans of the or each point embedding in or being urged against saidfixing.
 8. A non-removable protective cover as claimed in claim 1, inwhich the gripping means comprises cover gripping means, the covergripping means comprising the at least one second resilient arm.
 9. Anon-removable protective cover as claimed in claim 1, in which thegripping means comprises three generally flat arms.
 10. A non-removableprotective cover as claimed in claim 9, in which the arms define threenon-adjacent sides of a hexagon to receive a hexagonal nut/bolt headtherein.
 11. A method of protecting a joint fixing against excessiveheat comprises attaching a non-removable protective cover to the jointfixing by fixing gripping means for gripping the joint fixing, whichgripping means are resiliently biased to grip the joint fixing, saidresilient bias of the gripping means also allowing for expansion of thejoint fixing, and in which a heat resistant, fire resistant cover meansfor covering the joint fixing covers the gripping means and the jointfixing to protect the same from excessive heat, wherein the fixinggripping means comprises at least one first resilient arm comprising anend point directed away from an opening in the cover and radiallyinwardly toward the fixing, and at least one second resilient armcomprising an end point directed towards the opening in the cover andradially inwardly away from the fixing, wherein the end point of thefirst resilient arm is located closer to the opening than is the endpoint of the second resilient arm.